This application claims the priority of German application 197 21 613.7, filed May 23, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a press or a press arrangement having a transfer device for workpieces through the machining stations, driving and guiding devices for a gripper rail or for each of two gripper rails in the transfer, lifting/lowering, and optionally opening/closing movement axes.
Presses or press arrangements of the foregoing type have forming stations--machining stations--in which metal sheets are formed between mold halves by the movement of slides. The metal sheets, then constituting workpieces, are fed to the individual machining stations and are removed therefrom after forming. For this purpose, a transfer device which has driving and guiding devices for moving a gripper rail or generally two gripper rails in the axes of the transfer movement. The lifting and lowering movement, and, with a three-axis systems, also in the opening and closing movement.
The transmission of the lifting/lowering and opening/closing movements takes place in so-called closing boxes which are arranged, as it were, as "ground instruments" or as press-side devices in the area of the press stands but in each case must achieve the supporting of the gripper rails in areas which are remote from one another.
The use of direct driving devices, such as electric motors, on one hand, opens up new possibilities; mechanical devices for transmitting movements and for guiding moved parts are, on the other hand, absolutely necessary.
JP 59-197325 (A) shows a transfer device with motor drives for the transfer and the opening-closing movement. The lifting and lowering of the gripper rails would require separate measures or means. U.S. Pat. No. 3,010,587 shows a device for loading presses having an additional device for a vertical movement. A carriage can be moved horizontally toward and away from a fixed point. A link is rotationally movable on the carriage and, in its center area, is held by another link which is rotationally movable in the fixed point. The length of the pivot bearing in the fixed point to the bearing in the center point of this lever corresponds to half the length of the link disposed on the carriage. For avoiding the tilting of the table linked to this link, a second link system is required which has an identical construction.
EP 0 760 272 A1 also describes a positioning device with two carriages which can be moved in guides toward one another and away from one another. The carriages are movable by spindles rotationally driven by a motor and carry a pair of parallel control arms for the horizontal supporting of a table. The second carriage carries a control arm or a link which is also linked to the table. The control arms or links are rotationally movably disposed on the carriage and on the table. In order to be able to carry out an exactly vertically guided movement of the table, an absolute control of the motors rotationally driving the spindles is required in a reversible rotation.
An object of the invention is to adjust a gripper rail or, if present, two gripper rails in the many possibilities of basic adjustments and move them out of these basic adjustments, to achieve a precisely definable vertical movement.
This object has been achieved in accordance with the present invention by providing a transfer device in a press in which two carriages of a first and of a second type are assigned to a gripper rail or to each gripper rail if two gripper rails are used, and the carriages can be driven toward one another and away from one another, transversely to the actual transfer direction of the workpieces independently of one another. Two parallel control arms are rotatably disposed on a carriage of the first type and are rotatably disposed on the other end on a support part for a gripper rail. On the other carriage of the second type, a link is rotatably disposed which, on the other end, at half the length, is applied to one of the parallel control arms and is rotatably disposed there. The length of the link corresponds to half the length of the parallel control arm, relative to the spacing of their pivots. The support part is used directly as a longitudinal guide for a gripper rail, and if separate guiding devices are used, the support part is used indirectly for the bearing of the gripper rail.
One advantage of the present invention is the utilization of the upper support part as a direct bearing for the gripper rail or as an indirect part when additional bearing or guiding devices are used for the gripper rail. With respect to known closing-box solutions, however, the constructive measure of the bearing of spindles had to be carried out disadvantageously in the longitudinal course of the closing boxes.
Another advantageous feature of the present invention provides the advantage of common driving devices, in which case an option exists as to whether generally a drive should be provided for each spindle for the two carriages of a gripper rail.
Other advantageous aspects of the present invention are directed to a newly usable driving concept of the utilization of the linear motor principle. Although DE 195 06 079 A1 generally describes the linear motor principle with respect to the use for the movement axes of grippers on gripper rails, the present invention involves a recognition that this principle can also be used for the lifting and lowering of a guiding element for gripper rails by link control arms.